The permeabilities of reservoir rocks are generally determined by the measurement using gas or liquid flows. Such permeabilities are, however, considerably affected by fractures, laminae, veins, and so on. This fact necessitates the alternative method for the evaluation of true permeability. As eleven expressions, which are composed of the factors such as porosity, median pore radii and specific surface area, were scrutinized for the calculations of permeability, some of these expressions show excellent correspondences to air permeabilities of miscellaneous rocks as well as sandstones in the offshore Niigata. The calculation of permeability using the mercury porosimetry data is applicable not only to the fractured, laminated or veined rocks but to the extremely small rocks.Since the permeability is subject to petrophysical properties of rocks such as grain size, grain sorting, porosity, pore size, etc., it may be inadequete to consider that the lithological factor or tortuosity is always constant for all of sandstones. Based upon the petrographical and petrophysical investigations, the effect of specific surface area was taken into account to prescribe permeabilities in this study.It is theoretically proved that the isomedian-pore radius lines drawn in the specific surface area versus porosity plot assuming ideal porous media provide good coincidences in general to the result statistically determined by UCHIDA (1984).

In fireflooding, phenomena such as chemical reaction, heat and mass transfer, and phase change dominate the behavior, and these phenomena are influenced by the properties of a crude oil which is a mixture of numerous hydrocarbon components.In conventional mathematical models, the crude oil has been treated as a mixture of mostly 2 or 3 pure hydrocarbons, so that the properties of the crude oil are represented as those of the mixture of assumed components. This does not accurately simulate the vaporization-condensation phenomenon, as an example, which is one of the most important transportation mechanism of oil in the in-situ combustion.In our mathematical model, a crude oil is assumed to be a mixture of two hypothetical components, one of which can represent the lowest gravity component and the other the highest gravity component in the crude oil. It is also assumed that these two hypothetical components do not represent independently any other physico-chemical properties. Their fraction in the mixture is determined to express only the gravity of the oil and other physical properties are expressed as functions of temperature and pressure (and the gravity of hypothetical oil). The model presented in this paper is a 4 phase-7 component model. Balance equations are presented as Eqs. (1) to (10) and parameter equations are shown as Eqs. (11) to (65) in the text.

Distributions of sandstone around the Shiunji Gas Field differ significantly between the Shiiya and Nishiyama Stages, which is due to an abrupt change of basin topographies between the two stages. Sandstone in the former stage was accumulated at a deeper part of a monotonous slope-like basin by turbidites, whereas that of the latter was trapped mainly on a terrace-like basin through a well developed submarine canyon. The change of these depositonal areas, not to mention source areas, is considered to be ultimately controlled by differential movements of basement uplifts of this area.

Kakizaki Oki TSI-1, -2 and -3 wells were drilled during 1983 and 1984 on the Kakizaki Oki Structure, situated 10km offshore the town of Kakizaki between Kashiwazaki city and the Kubiki Oil/Gas Field. In the Kakizaki Oki TSI-2 well, cores totalling 50m were taken from the III bed group and the IVa bed, which are the upper most part of the lower Teradomari Formation.This paper studies the sedimentary environment and the reservoir quality of cores, and lithofacies distribution of the III bed group and IVa bed. These beds are of middle bathyal and/or deeper paleo water-depth from paleontological data, and they correspond to mid fan deposits for a submarine fan model proposed by WALKER (1978). Sandstones in core samples, taken from IIIc+d/IIIf beds and IIIg/IVa beds in descending order, are situated at the site of smooth portion of suprafan lobes on mid fan and at the site of braided channels around upper fan to mid fan deposits respectively. Sandstone cores from the smooth portion of suprafan lobes show good reservoir quality in terms of porosity (φHe), permeability (Kair) and pore geometry. On the other hand, ones at braided channels mainly show poor reservoir quality.Intergranular pores, the major pore type, are observed largely in IIIc+d/IIIf beds and are less common in IIIg/IVa beds which were cemented and compacted.“Micro pores”, found as intra-kaolinite cement pores and intra-matrix pores, are markedly recognized in IIIg/IVa beds. In IIIg/IVa beds, primary features and diagenetic changes in textures cause low permeability and a difference in the distribution of pore types.A cosiderable amount of oil was discovered in the III and IV beds, but only in the TSI-1 well. Although core samples from the TSI-2 well correlated to oil-bearing horizones in the TSI-1 well showed good reservoir quality, only small amount of oil and gas was recognized by the production tests. One factor for poor productivity is assumed to be the low relative oil permeability in a high water saturated state.

The rudist reefal limestone complex of the Mishrif Formation in the Umm Al-Dalkh Field, offshore Abu Dhabi, was divided into several lithofacies from petrographic analysis and electrical log interpretation in the early development stage of the field. To grasp complex distribution of these lithofacies and to construct a three-dimensional geological model of the limestone complex, a technique using seismic impedance analysis was applied.Fifteen seismic impedance sections and synthetic impedance logs of twenty five wells were prepared. Lithofacies interpretation of the seismic impedance sections was carried out over the field area through correlating to the synthetic impedance logs incorporated with the petrographically derived lithofacies data.A geological model of the Mishrif Formation obtained by this method indicates that there were four main stages of reefal development and after the last stage, erosion took place in the central build-up area. It is suggested that there is a close similarity between this model and the occurrence of recent reefs in the Arabian Gulf.

The Mauddud member consists of a predominantly carbonate section with subordinate terrigenous intervals. Its age is esentially late Albian, except for its uppermost part, which at least, in Dorra field, is possibly early Cenomanian.The sedimentation of the Mauddud member is the result of a regional transgression which developed from the northeast to the southwest and did not take place contemporaneously all over the studied area.The Maudded transgression took place in three main phase. A first phase is recognizable in only the eastern and north-eastern part of the reviewed area, Dorra field. A second phase extended more largely southward, reaching Hout field. A third, final phase extended all over the reviewed area.The Mauddud transgression ended up with the sedimentation of the Wara member, which brought back terrigenous facies all over the studied area.

Sedimentary facies, environment and diagenesis which control reservoir characteristics of the Lower Cretaceous Thamama Zone IVA in the Mubarras Field, offshore Abu Dhabi, United Arab Emirates, were studied by analyzing cores of about 380 feet (115.8m) from 8 wells.Six different carbonate lithofacies have been identified in the Thamama Zone IVA. These lithofacies are (1) algal peloidal grainstone/packstone/wackestone, (2) peloidal grainstone, (3) intraclastic grainstone, (4) peloidal bioclastic packstone/wackestone, (5) bioclastic peloidal packstone and (6) orbitolinid wackestone/mudstone. Peloidal grainstones have the best reservoir characteristics (porositypermeability) among them. The Thamama Zone IVA is overlain by argillaceous bioclastic wackestone which acts as cap rock of the reservoir.The depositional environment of the Thamama Zone IVA has been interpreted as being of lagoon to near-barrier in a shallow shelf condition. Grain-supported textures (grainstone and packstone) dominating in the northern part of the Mubarras Field suggest relatively high water energy such as near-barrier environment. On the other hand mud-supported textures (wackestone and mudstone) dominating in the southern part of the field suggest quiet water such as lagoonal environment.The main diagenetic features in the Thamama Zone IVA are micritization, leaching, cementation, dolomitization and stylolitization. Cementation especially by ferroan calcite deteriorates reservoir characteristics. The occurrence of this cement is limited within and close to the argillaceous limestones. This phenomenon suggests that the argillaceous limestones play an important role for the cementation by ferroan calcite.

Upper Jurassic Arab Formation consists of evaporite and carbonate sediments deposited in the Arabian platform. From the observation of slubed cores and thin sections of the Arab Formation of 13 wells in offshore, Abu Dhabi, six types of carbonate rock facies have been determined. These are 1) algal mat mudstone and boundstone; 2) bioturbated wackestone and packstone, 3) peloidal bioclastic intraclastic grainstone and packstone, 4) bioclastic wackestone, packstone and boundstone, 5) well sorted oolitic peloidal grainstone, and 6) peloidal bioclastic wackestone and mudstone. Former three of these six rock facies were formed in the tidal flat environment. These are intercalated with anhydrite layers and occasionally dolomitized. Later three formed in the shallow shelf and lagoonal environments. The stratigraphic relationship and distribution of those rock facies in the Arab, Formation show the shallowing upward sequence from the shallow open marine carbonate shelf to supratidal environments.